Ocular motor tests in relapsing remitting multiple sclerosis

Abstract

Background Multiple sclerosis (MS) is the quintessential neurologic disorder from which one can gain insights into the principles of afferent and efferent neuro-ophthalmology. The popularity of eye movements as an experimental tool can be partly attributed to the fact that they can be conveniently and accurately measured and analyzed, and also because much is known about their neural substrate. It is therefore no surprise that eye movements have been commonly applied to better understand the visual and motor disorders in patients with MS. Objectives The aim of this study was to demonstrate the vast ocular motor abnormalities that occur in this disease using videonystagmography as our tool of description and determine the relationship with Expanded Disability Status Scale (EDSS) and MRI findings. Materials and methods The current study included 76 patients who were divided into two groups. Group I comprised 54 patients with relapsing-remitting multiple sclerosis who fulfilled the Revised Mcdonald's criteria for diagnosis of MS. The age of the patients in group I ranged from 20 to 68 years, with a mean of 35.13 ± 9.42 SD (23 men and 31 women). Group II comprised 22 healthy age-matched and sex-matched individuals who were recruited from the general population and were not relatives of the patients. Their ages ranged from 19 to 54 years, with a mean of 33.81 years ± 10.07 SD (11 men and 11 women). Video-nystagmography, saccadic tracking, random horizontal saccades, optokinetic tracking (at 20, 40, and 60΀/s), smooth pursuit (0.2, 0.3, 0.4, 0.5, 0.6, and 0.7 Hz), and gaze-evoked nystagmus were examined in both groups. Group I, in addition, was subjected to a thorough neurological history and neurological examination, EDSS assessment, ophthalmologic examination (visual acuity and ocular motility), and radiological assessment by MRI with and without contrast. Results The eye movement disorders most commonly noted are saccadic dysmetria, followed by gaze-evoked nystagmus and pendular nystagmus. They are caused by disease affecting the brain stem and cerebellar circuits. Reduced pursuit gain and saccadic pursuit were also noted. A strong correlation between brainstem and cerebellar MRI lesions and the affection of the ocular motor system was well noted. A high EDSS score was well correlated with abnormal ocular motor test findings. Conclusion Ocular motor system tests are more sensitive than conventional clinical examinations in identifying abnormalities in MS.